Corrosion resistant article



Patented Jan. 16, 1934 UNITED STATES CORROSION RESISTANT ARTICLE Frederick M. Becket, New York, N. Y., assignor to Electra Metallurgical Company, a corporation of West Virginia No Drawing.

Original application April 29,

1930, Serial No. 448,428. Divided and this application October 29, 1932. Serial No. 640,339

2 Claims. (Cl. 196-133) To increase the resistance of iron to corrosion and to oxidation at elevated temperatures it is customary to incorporate chromium in various quantities. When the chromium content rises to about eighteen per cent or higher with the carbon content suitably low, alloys are produced which have a wide field of application due to their excellent resistance to various corrosive infiuences. These alloys, however, tend to be deficient in workability and they do not possess the physical properties required to adapt them to severe deep drawing operations.

It has been proposed and has become a common practice to incorporate a content of nickel, for example eight to fifteen per cent, with such a corrosion-resistant iron-chromium base in order to enhance the working properties. This expedient is quite effective for the purpose referred to and the iron-chromium-nickel compositions have gone into extensive use. It has been found, however, that the incorporation of nickel markedly diminished the ability of the metal to withstand the action of sulphur dioxide, hydrogen sulphide and other sulphur compo'mds, and in certain applications where sulphur compounds are encountered at elevated temperatures and where a high degree of ductility should be preserved, neither the binary iron-chromium alloy nor the ternary iron-chromium-nickel alloy meets the requirements.

I have found that a high degree of workability can be imparted to corrosion resistant ironchromium alloys by appropriate additions of manganese-and that unlike nickel the manganese does not appear to impair the resistance to corrosion in any respect. In comparative tests the iron-chromium-manganese alloys are found to resist the action of such agents as sulphurous acid and moist hydrogen sulphide at ordinary and elevated temperatures, substantially-to the same degree as the most resistant'binary chrome irons, and far better than any iron-chromenickel alloys which have come to my attention.

The best properties are exhibited by alloys containing from about fifteen to about twentytwo per cent 'of chromium. To develop the maximum degree of workability I prefer a proportion of manganese within the range embraced between the'approximate limits of six per cent and sixteen per cent. More manganese may be added but it will not as a rule bring about an improvement in properties suflicient to warrant the additional expense.- The iron-chromiummanganese alloys are discussed in more detail in my application Serial No. 435,957, filed March 14, 1930, Patent No. 1,920,953, granted August 8, 1933. As is there stated the workability of the alloy increases as the carbon content is diminished, and where severe working operations are contemplated the carbon content should not be above about three tenths per cent and is preferably below twelve hundredths per cent.

A principal field of application for the herein described alloys is in the thermal decomposition of hydrocarbon material, for example the cracking of petroleum fractions to produce gasoline. Such decompositions are ordinarily carried out in tubes and the latter may be subjected at a high temperatureto oxidizing conditions on the outside and simultaneously to the action of sulphur compounds associated with the material being cracked and contained within the tubes. The alloys are in all respects admirably adapted to the fabrication of tubes for such operations, and they are equally suitably for making the tubular condensers in which the cracked products are usually liquefied.

This application is a division of a prior application, Serial Number 448,428, filed April 29, 1930.

I claim:

1. Anoil cracking tube composed of a ferrous alloy containing about 16% to 22% of chromium, about 6% to 16% of manganese, and carbon, the carbon content being not more than about 0.3%, and the balance being substantially all iron.

2. An oil cracking tube composed of a ferrous alloy containing about 16% to 22% of chromium,v about 6% to 16% of manganese, and carbon, the carbon content being not more than about 0.12%, and the balance being substantially all iron.

FREDERICK M. BECKET. 

